Telephone repeating system.



E. GRISSINGHL TELEPHONE REPEATING SYSTEM.

APPLICATION FILED JUNE 3.1916.

Patented Mar. 20, 1917.

2 SHEETS-SHEET 1.

IN VEN T0 E. GRISSINGER..

TELEPHONE REP EATlNG-SYSTEM.

APPLICATION FILED JUNE 3. 1916.

Patented Mar. 20, 1917.

2 SHEETSSHEET 2.

' UNITED, STATES PATENT ELWOOD GRISSINGER, OF BUFFALO, N YORK, ASSIGNOR TO AMERICAN TELEPHGNE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

' To all whom it may concern:

a specification.

j TELEPHONE REPEA'IING SYSTEM.

Be it known that I, ELwoon GRISSINGER,

a.eitizen of the United States, and resident of Buffalo, in the county of Erie and State of New York, have invented certain new and useful Improvements in Telephone Re peating Systems, of which the following is This invention relates to telephonic speech transmission, with particular over'which speech'can be successfully transmitted or the improvement in the efficiency of'existing transmission circuits or both, coupled with the ability to reduce the investment and'maintenance cost of transmission lines for the transmission of speech.

One object of-the invention is to provide telephone repeaters in. which the difference in phase between the exciting sented by speech waves) and the displacement of the vibratory system is controlled within'a desired range.

Another object is to provide a reciprocal talking telephonic repeating circuit with twin repeaters, the repeaters so .constructed i and related to oneanotherthat, in respect to the' displacement of the vibratory element of each repeater under the influence of speech Waves (exciting. forces), the rela- 1 tive differences .in phase between the displacement of the vibratory system and the exciting force in each repeater w ll be approximately neutralized with reference to one another. j Another object is to provide a repeater for a reciprocal talking telephonic repeating circuit employing a single repeaterconnected in"booster relation; the repeater .so constructed that, in respect to the displacement of'its vibratory element under physical movements I or .vibrations corre the influence of speech waves '(exciting forces), the difference in-phase between the two will be such that the wave forms generatedby the repeater because of the movement of its vibratory element, will the more closelycoincide and hence be the more'ne'arly accurately phased with the original waves traversing the main line circuit.

I employ repeater apparatus of the "electromagnet-microphone type inwhich the,

mechanical vibrator or vibratory system has reference to long distance working; and it has for its. object the increase in the length of lines force (repre-' which patentsI have carefully theory and practice of the fundamental,

tion and Fig. 2 is a top I Specification of Letters Patent. Patented Man 20 1917. Application filed June 3, 1916. Serial No. 101,453.

period or natural frequency of free mechanical. vibration. Hence it will 'resonate strongly in response to exciting forces of frequencies approximating the natural frequency', and the resonant response will be greater according as the frequency of the exciting force more nearly approaches said natural frequency. Moreover, tion is' such that the vibratory system behaves like a theoretical vibratory system having only one degree of freedom, in that it has only one natural frequency range or region of resonant response below 2000 periods per second. Preferably, it is approximately 1000 periods or more per second. here the repeaters are used in pairs they are constructed so that the corresponding parts of their respectivevibratory system are substantially identical. Reference is made here to my Patents N 0. 1,203,325, dated October 31, 1916; No; 1,203,326, October 31, 191 6; bra-1,198,345, September 12,1916; and No. 1,205,618, November 21, 1916, on telephone repeaters and transmitters; in outlined the characteristics of the vibratory elements of my constructelephone apparatus. The present inven tion is closely related to thesame subjects matten Other features and objects of my inven-,

tion will be evident from the following decompanying drawings in which p Y Figure 1 is a side elevation partly in .secplan view of a repeater adapted for the practice of my present invention.

Fig. 3 isa face view of details of the mi-, crophone shown inFig. 1,

. Fig. 4 is a detailed vertical section through a microphone cell similar to that shownin' Fig. 1, but illustrating a difi'erent form of elastic suspension for the vibratory elementof the microphone,

Fig. 5 is a face view illustrating a-third form of suspension of the microphone cell, Fig. 6 is a diagram illustrating some of the principles of my invention,"

Fig. 7 1s a diagram of a complete recip rocal two-repeater circuit in accordance with my present invention,

Figs. 8 and 9 are diagrams illustrating a modified arrangement oi a repeater in booster relation to its circuit.

ever in certain details of the microphone cell and the vibratory element therein. This repeater structure includes a relatively rigid base 1, of brassor similar material, standards 2 and 3 each carrying magnets preferably of-the telephone receiver type having oppositely arranged pairs of poles and 5-5, energized by coils 6 -6 and 7'. These magnets are carried by solid slides, as 8, which are accuratelyguided in said standards and adjustable by the screw threaded extensions 9 engaging nuts 1U, swiveled in the stationary supports 11. Th se magnetsraiford a balanced magnetic fielc for the vibratory member of the microphone cell which is interposed between them. The microphone cell is mounted in a I standard of which the base section 12 and the top section 13 'are secured by screws 14 constituting a circular clamping support for the rings 15, which, in turn, support and laterally clamp the microphone cell by means of screws, one of which is shown at -16.

The microphone cell has been designed to 1 give compactness in structure, ease of assembly, cheapness of construction and what is more important, a material reduction in the mass or inertia of the movable element thereof.

It is composed of a central annulus 17 threaded eXteriorly and .made of bakelite or a similar insulating compound or synthetic composition. Caps 18-18 of the same compound are threaded one upon each end of the part 17. The part 17 has a central opening and two .oppositely disposed recesses. In the recesses, carbon disks 19 are seated. These carbon disks are of such thickness as to be practically nonvibratory. Each such carbon disk has a clearance aperture 20, somewhat larger than the diameter of an aluminum lock nut 21. Each such carbon disk has also the clearance holes 22 placed there for the purpose of increasingthe sensitiveness of the microphonicelement and also to prevent what is usually'termed packing. The outer side of each disk 19 is covered with a soft thin silken disk 23 having a central opening 24. The silken disk is used for the purpose of preventing the carbon granules in the resistance chamber from coming through the holes 22. The central opening 2 1 of the silken disk is made just large enough so that it will fit closely over the aluminum lock nut 21. If desired,

the silken disk could be dispensed with and a thin mica or. other moisture proof diaphragm 26 for the purpose of properly inclosing the. microphonijc element chamber and making the same airtight and moisture proof. On the outside of the mica diaphram 26 is placed a clamping ring 27. All of the parts 19, 25, 26 and 27 are securely and rigidly held in the annulus 17 by means of the ca s 18. The inner side of the carbon disk 19 is highly polished.

A central carbon electrode 28, highly polished on both sides is mounted on a threaded aluminum alloy rod 29. A central hole in the carbon electrode is provided for this purpose. Clearance holes 30 are also placed in this central carbon electrode for the same reasons as stated for the clearance in the stationary carbon electo bind the diaphragms 26 to the lock nuts 21 and thus support the movable electrode in the center of the microphonic chamber. The. spacers and washers noted as 25 and 27 may be made of metal, in which event leading in wires as 33 and 34: passing through openings in the part 17 are soldered to them constituting terminals of the primary or local circuit of the "ariable resistance medium. If the rings as 25 or 27 are made of bakelite or similar non-conducting material as they may well be, then, the edge of-thecarbon disks 19 are preferably electroplated with copper, to which part, the leading in wires 38 and 341 can be soldered.

The complete element can be mounted in any of the suspension rings which I'have shown in mypatents, with the only dilference that the rod 29 in the type shown herein need not be insulated from the rings, but may constitute a common electric terminal with said rings or with the base of the instrument. The two loads 33 and 34, are however, insulated from the ringsand from the base of the instrument. Conducting connections for the purpose of carrying current to the movable electrodes are'omitted in this design and lightness of weight for the vibrator-is secured by using a single all carbon electrode. A further reduction in mass may be secured bymaking the movable electrode 28 in the form of a sector Without sacrificingother qualities of. the microphonic element.

The caps 18- may be sealed to 17 and to the.

rings 27 and the rings-27 may be sealed to its periphery at one-side with projections or lugs 37'. These projections have circular 4 apertures through them to receive the enthe outer Imicav diaphragms26. The nuts 31'32 can be sealed to the rod 29 and to the mica d-iaphragms. For this' purpose I have successfully employed flexible collodion.

This sealing-is done to make the chamber airtight and moisture proof.

When in operative condition the granular variable resistance chamber is about.

half filled with granular carbon or some other similar variable. resistance medium.

The means utilized in this form of transmitting element for a telephone repeater to raise the free period of the vibratory element to a desired periodicity, preferably approximating 1000 P. P. S. or greater, is a rod or equivalent member resisting displacement through torsional tendencies. The construction herein referred to comprises the rings 15', having the screwslfi for the fastening of one ring to another and the terminal blocks 35 havingelectrical COIHIQC-r tions such as 36. The ring is provided near larged portions or fixed diametersof torsion rod or tube 38. As more fully exlained in my Patent No..1,205,618, the enargedportions of the torsion member have vapertures extending througlr them so that such parts of the torsion member -can be securely and rigidly fastened within the lugs 37 by means of screws 39 passing through the torsion member and engaging the lugs 87. The torsion member-is also formed with a centralportion of enlarged diameter with an aperture extending therethrough- Be tween the enlarged diameters the torsion member takes on a smaller diameter such as 40. A webbed leverage member'41', made .from' preferably an aluminum alloy and having a circular aperture in its free end, is securely and rigidly fastened to the enlarged diameter of the torsion member by a driving fit of the slightly tapered shank 42. torsion member being securely fastened to the lugs 37 on the rings 27 any displacement of the smaller free end of the lever 41 is resisted by the torsional tendencies of the sections 40 of the torsion member. The lever and the torsion member being substantially stantially 'prior patents;

The

rigid' against transverse flexing or wab-.

bling, and all the elastic flexing being subof the members 41-41, moving the companion nuts in either event correspondingly.

By designing the torsion member properly with relation to the mass and inertia of the entire essential vibrating system, the resultant freeperiod of such vibratory system can be made to equal or exceed 1000 P. P, S. The precaution to. beobserved is that there shall be no flexure-in the member 41 or in the unclamped portions of the torsion rod 38. It'is believed that the remaining operative characteristics of such a transmitting element have been fully set forth in my In Fig. 4, I have shown an arrangement wherein the transverse bending stress of a pair of ste'elpins 45-45 is used as the elastic element of the vibratory electrode system, the remaining parts of the structure being substantially the same, having sub-. stantially similar functions, methods of adjustment and uses.

. In Fig. 5, I have shown an arrangement of stretched wires for. giving-the vibratory system a definite frequency. The structure is substantially identical with that shown in, Fig.5 of my Patent No. 1,198.345. In

this case, the microphone supporting ring is provided at its lower side with a screw 46 which is-threaded intothe case and'projects above the surface where it carries a hardened steel. grooved roller. The top of the ring is provided :with a pair of hardened steel tapered pins 47 fitting corre sponding recesses in the frame and pro vided at their outer ends with capstan heads 48. Each of the pins 47 has a transverse aperture 49 receiving the end of a steel piano wire 50 which .extends around the roller on screw 46. The outer face of the frame is provided with four lugs 51 within each of which there is an adjusting screw 52. Each of the adjusting screws 52 has in its end an opening to receive a cylindrical hardened steel pin 53 'which is free to rotate thereinand which has in its end a groove to receive the piano wire 50.

The parallel wires areclamped by the nuts 4344 on the threaded rod 29 of the mi,crophone vibrator element. In this device, the tension can be adjusted by varying the lateral pressure of the screws without length,

will have substantially the same free period.

-wires of a pair lie in the same plane,

' periodicity ,The exciting coils 6,

. tone is low,

'tutemeans the necessity of changing the position of the lock nuts on the vibrator although the latter may be also adjusted after the manner described in connection with Fig. 1.

In assembling the parts and adjusting the wires, care should be taken that 'the tlw'o t rat the two pairs liein parallel planes; also the wires and the sections thereof above and below the nuts 13 and H should be of equivalent, (and preferably exactly similar) weight and tension, so that they or natural frequency. @therwise the simple harmonic character of the free vibrations of the system may be impaired by the introduction of other frequency components which may causea plurality of regions of resonant response, and may give rise to one or more beat frequencies which may produce disturbing audible effects at the.

receivers.

These various elastic suspension means which are capable of giving the desired to the vibratory-system are utilized in' connection with the further feature 'of' my inyention which isdescribed hereafter. I

In Fig. 6 I have diagrammatically indicated one form of my said telephone repeaters with its local. circuit. The local electrical circuit is made up of, a battery 122 and the differentially connected primary winding 123 of an induction coil. The secondary winding 12l of the induction coil is connected to" leads 125-126. 7 on the magnets-Li, 5 areconnected together by the wire let and to leads 114-415. i

If the local battery circuit is completed and we then connect the lead 125 to 114: and 126 to 115, the repeater, if adjusted, will emit a'steady tone. If the pitch of this it will be found that, upon reversing the polarity of the battery or reversing the connections of the wires 125 126 to 11el-115, the tone will change to one of higher pitch. The phenomena isexplainable by the difference in phase between the physical displacement of the vibratory system and the exciting force represented by' the current wave traversing the coils 6, 7 The object of this part of the invention is to recitethe above giving the cause and effect and then to show a means of controlling such phase displacement within desirable limits.

In each of the forms of telephone re- (stiffness) of the'yibratory system constlfor controlling such phase dis- Because, =1f we assume a conplacement.

to the movable system, then for stant mass each change made in the free period of the I the wire suspension, altered by means of assembly,. or

This will be shown to tive advantages respecting a form of phase vibratory element, we will alter the phase displacement referred to. In the case of the free-period can be the initial tension 'on the wires and further, wlien such initial ten sion is given, additional alterations in .the tension can be effected by bowing the wires inward or outward or by bringing them closer together, or by both thelast named means. In the torsional device, the free period can be altered by imposing initial torsional strains on the torsional member accomplishing this bymoving the lever arm attached to the torsional member'inwai'd or outward along the. threaded rod aided by] the threaded nuts. sition of such phenomena in connection with A mathematical expothe dynamics of elastic bodies will be found 7 in The Dynamics of Particles and of Rigid, Elastic and Fluid BodiesfiA \Vebster, second edition, Teubner-Leipzig,

(a) The free vibration has its period determined solely by the nature of the system.

The forced vibration takes the l the force.

(b) If there is tion dies away, while the persists unchanged.

The motion of any system possessing a damping, the free vibradegrees of freedom (more than one) slightly brating system need not be higher than 1000 P. P. S., because that is above any .ofthe period of forced vibration 1912, pages 152 to 155, section 4:1. 'It being there shown that- 1 tween the vibrating system and the exciting dominant frequencies of articulate speech.

The precise angular phase displacement may bevaried between wide limits for articulate speech and still have the proper free period to the system. However,.as we increase inertia, we must increase stiffness and as we increase stifiness ,we lose volume of transformed energy for the same primary volume; Conversely, as we decrease inertia, we can increase power, struction difficult to assemble and lacking in qualities of permanencyof adjustment. Nevertheless, as already pointed out, my constructions permit of a control of the phase displacementeither by original design and possess certain operadisplacement in a two wire reciprocal-talkby subsequent adjustment.

but we then approach a conin'g telephone repeating circuit employing twin repeaters as already disclosed in cer 4 taln of my patents. It is believed tobeunspectively, electrical characteristics as the section D and necessary for me to explain in detail how the circuit: operates for reciprocal. talking as.

that has already been done. What it is desired to refer to here is the effect which the difiereiice in phase between the displacement of the vibratory system and the exciting forces in the relay magnets has upon the behavior tions.

. With respect to the circuit as shown in Fig. 7, it is sulficient to say that A and B are of the circuit under certain condisubscribers stations at distant, ends of a long distance line requiring the use of repeaters. The line between the stations is divided at a relay station C intotwo sections D and E. The line sections D and E have current and phase balancing extensions 15 and G rethe extension F having the same the extension G having the same electrical characteristics as the line section E. The air" tificial resistance,

inductance and capacity elements necessary for this purpose may be distributed in groups so as to simulate the distributed characteristics of the real line with any required degree of accuracy. The

- neutralize the efi'ect of the wave forms from j 'the'output side of one repeater upon the intwm-repeater circuits are inductively con'- nected between the sections at the. neutral or balancin points of each in such'manner as not to dlsturb that balance, the connection being through the medium of three-limb. re-

peatingcoils which are connected so as to put side of the other repeater. The further ciently details of such circuit. and its method of operation are fully set forth in my Patents No. 1,198,212 and No. 1,198,214, dated Sep-' tember 12,1916.

It is assumed that in the circuit shown in Fig. 7, the two repeaters are adjusted to sensibility or maximum power and that in this condition they are operating on a telephone circuit of appreciable length. The balancing sections have been designed as fitting the main circuit sections witha reasonable degree of approximation; as a result whereofv tendency tp hang on as it were. An examination or an adjustment of the repeatersfor the singing test as described in' connection with Fig. 6 may show that each repeater.

will emit a short circuit tbne of approximately the same pitch. Then if we reverse the leads of the exciting coils or the polarityof the localbattery supply for either of the repeaters, .it will be found thatthe above tendency tohang on will no longer exist.

What hats been done to correct the above describedtendency has been merely-to neutralize the efiects of phase displacements in the individual repeaters among themselves. The

net result is that for constant repeater power, the circuit will stand a greater degree' ofunbalancing or, in other words, the degree of balancing need not be-so accurate.

oreover, repeatersof large volume can be used on shorter circuits than would otherwise be the case. At the same time, the flexibility of this arrangement will take care 6" wide variations'in actual .mainline condi' tions upon either side ofa repeating station.

' The preferred. form of circuit (Fig. 7) is that in which there isutilized the method of so connecting twin. repeaters in a reciprocal circuit, that they shall opposite phase relation.

be in individually fThe above explained theory and limita-' tions respecting a form of phase displace-.,

ment is madeuse of herein connection with the circult shown 1n F lgs. Sand 9- wh1ch 1s a two wire reciprocal talking telephone circuit, using a single repeater in what is commonlytermed booster or bridged. h

There is the usual repeater device 216 with its exciting coils bridged across the'two line wires in a manner similar to that shown in the figure. A battery 217 supplies local energy to, the repeater through primary Winding 218 of the repeater induction coil. There is'a multiple (four winding) secondrelation, branched i ary winding'on the repeater induction coil inductively related with the primary .wi-nd- I ing. The terminals of the different secondary windings are connected .as shown in Figs. 8 and 9.. It.wi ll be assumed that the line' wires-208209 lead'to one subscriber and 21 1215. to another. Themaincircuit sections on each side of the bridge connection of the repeater coils must have approximately the. same electrical that when the amplified waves from the re.- peater are inductively transferred to the main line through the four secondary winds ings of; the induction coil and ar'e thussli perposed on the original waves traversing the main line,

nectionof the repeater exciting3coils.1, It is also necessarv that the phase' relations of k the new waves shall approximately coincide with the original. In a real line, however,

characteristics .so

there willremain approximately zero potential across the bridge conthe characteristics of the two main line sec- '7 tions will not usually be the. samev and while the zerojpotenti'al ancing to get equal similar electrical rea'ctanc'es along the respective main line sectionsand the unavoidable phase displacement attend-" can be secured by bal-.

current values, thedisdistributed 25 of the vibratory element of the repeater with sufiicient accuracy by merely balanclng the electrical characterforce for the essential v transformer react-ions in the induction coilrender it impossible to superpose the amplified waves on the original waves of phase relation,

ing the istics of the two main line sections; and my present invention involves recognition -0 and correction for the inherent difference in phase displacement between the vibratory system of the repeater and its exciting wave forms of articulate speech. This correction considers inertia, resistance to displacement and free period. By properly proportioning the reeater parts so as to keep the free period at 1000 P. P. S., or over, the phase displacement can be controlled sufficiently to bring about an electrical phase relation at the "repeater terminalsof such a character as to minimize distortion of the wave forms which otherwise exists.

The proper proportioningin accordance with the principles disclosed above consists in varying the values of elasticity (stiffness) and inertia which determine the frequency vibration,

without impairing its quality of .which, as I have stated, is practically like that of a theoretical vibratory system having a single degree of freedom, and without, unduly lowering the natural frequency of 'the vibrator, whic as before stated is preferably 1000 periocs per second, or more. In practice, the desiredresult may be achieved by employing a vibratory armature-electrode structure of the proportions shown in Fig. 1 made of the materials and or natural elastic vibration.

repeater may construction described above and weighing say 10 or 15 grams.

Such a vibrator will insure minimum inertia with maximum efficiency. The elastic member (torsion rod, flexing pin'or stretched wires) will then be designed and adjusted for the minimum stiffness necessary to impart to the system the necessary high frequency The repeater may'then be connected intoits shunt across the line, and the current balance giving equal potential and zero current across the shunt secured by inserting a suitable noninductive resistance or resistances in the main line connection to the shunt. The correctness or incorrectness of the phase re, lation between the main line wave forms an the amplified wave forms flowing from the be determined by -ear test for clearness of articulation. If the transmitted speech is clear, it will be understood that tie proper values for elasticity and inertia above described until clear, thus showing that the amplified waves of the vibratory member of the repeater were correctly hit upon at'first trial. Otherwise, however, the elasticity (stiffness) may be gradually increased-in any of the ways articulation becomes approximating original exciting current.

at wh1ch the oscillographs show that there-' of free period from the repeater are correctly superposed upon the waves in the line, It is of course, conceivably possible to make the vibrator of adjustable weight and to change the inertia stiffness ratio by decreasing the weight, but in practice,

it is far preferable to make the vibrator of as small mass as pos sultant wave most nearly approximates simple harmonic form at the 1000 frequency.

will be approximately correct for use in connection with the human speech waves of the real line across which the repeater .is to be connected in booster relation.

It will be noted that this latter procedure .is more difficult in practice and less satisfactory in result than that described for the two-way talking two-repeater sectional circuit shown in Fig. -7, in which the phase relation adjustment of the repeaters can always'be effected with perfect accuracy at the factory by simply tuning the vibratory systems of all the repeatersto the same natural frequency.- This tuning may be faciliand causing them to sing., that is, emit a continuous audible note. This singing note will be of high or low pitch according to how the circuit connections are made and when either the high note or the low note tated' by short circuiting the instruments is produced, the other note may be produced from the same repeater by merely reversing the terminal connections either of the battery or of the short circuiting connection. The higher of the tWo notes is always approximately thesame pitch or frequency as the natural frequency of the vibratory very convenient indication whereby the vi.- bratory system of a repeater may be tuned to a desiredhigh pitch" and the several repeaters very accurately tuned to the same p1tch. I d stinguish between I same pitch and high p tch because so far as concerns compensating or balancing the phase displacement in one repeater. against the phase displacement of the other, the, definite simple harmonic character of the vibration and the identities of the frequencies rather than their numerical values, are the important factors. The high pitch (say 1000 per second) is preferable for the entirely distinct .system and hence the sound furnishes a reason 'explaiifed "elsewhere,' namely, it

1 brings the region of mechanical resonance above the important frequencies of human speech and so avoids the undue resonant magnification of anyof them. I

The vibrators of all the repeatersbeing I thus tuned to the same natural frequency,

they are ready to be connected in pairs fin the repeater circuits between the phase balanced line sectionsat each repeater station, a the only precaution-being the reversal of the battery or line connections of the onerepeater with respect to those of the other, so that if caused to sing, as by extreme un balancing. of the line sections, one repeater will sing in the characteristic high note while v the other will sing in the characteristic low l noteso that when both are singing, the result will be a composite of botlrnotesr ents Wlll result "111 a perfect compensation or balance of the phase displacement of the Th'e'se two simple easily practised expedi one repeater with respect to the phase displacement of'the other repeater of the same pair, and they are expedients which may be practised even-by'mecha-nics or electricians having no understanding or conception of ,1nvolved I V Referring again to the booster arrangethe complicated mechanical' and. electrical principles and quantitative values actually ment of ,repeater described iii-connection with Fig. 8, the best'results can be secured I only by utilizing-in thisconnection the dis-,

covery which I have made with respect -to all circuits in whichthejrepeater is used in boosterrelation, namely the superposition of the waves from the repeater, on the originalwaves, cannot be. equally perfect for talking in both directionsfunless the two subscribers. stations at opposite ends of the lines are identically arranged and identically connected tothe'mainlinewires'as to A all their parts and particularly as to the polaritiesbf the local batteries and direc t'ionof-fiow ofthe currents through the primaries of the usual repeating-coils at the 'sub'scribers station, as well as the connections of the secondaries ofsaid repeating coils to their respective sidesofthe line. Sofar as these polarity relations can be 111-:

dicated diagram, they will be; covered by taking the subsribers' station as shown 'a't-:A, Fig. 7 with its main line connections D and jconnecting directly and without any transposition of terminals to'the wires'214,

215 of Fig.'"8'and by taking thelocal sub- 1'. scribers station B Fig. 7 andsimilarly conv 1 a nectin'g its ma n line wires E to wires 208,

i209, Fig.8, -I mention this because infpresent commercial telephone practice, has not'been the custom to pay any attention to "preserving identical character'and polarity -']of the connections of these parts andwhere repeaters have beenused in boosterrelatipn either one of the two vtem of Fig. 7 is particularly on such circuits {the result has always been that the articulation was poorer in one direction than in the other.

Even when the subscribers sets are identically organized and connected as above described there is still the possibility that the connections at switch boards orother points in the "main line may be such as to give possible polarity re-. lations of the two sets with reference to each other and to the line. It is important that these connections be always the same since upon which of the two ways theconnections are made will depend whether the booster repeater should have its battery and recelving coils connected for the high pitch howling tendency, or the low pitch howling tendency which Ihave explained above as characteristic of, these repeaters. In practice, the fact as to which tendency is' required for the repeater connection, is mostv simple and easily determined by trying the repeater'with' a battery connected one way in the circuit and then. trying it with the poles reversed, and noting which connection gives the best articulation. Because, however perfect or imperfect may be the clasticity adjustment of the repeater for any given adjustment, the articulation will always be better when the correct howling tendency connection has been selected. Once the repeateriis correctly connected and cor-' rectly adjusted, it is necessary to see to it I that the line connections be not subsequently reversed. i v

The booster system shown in Fig. 8 may be used on short lines where only one repeater station'is required and the divided section phase balanced twin repeater sysadapted for use where a line is long enough to require subdivision intoseveral sections with several repeater stations.

I would nevertheless size the fact that thesystein of Fig. 7, when organized in accordance with all of the novel features of construction, adjustment and coordination of parts hereinabove described,

is preminently adapted for indefinite ex- .pansion and that I-have long since successfully used as many as six successive currentioo particularly emphai 60 tension to ralse the frequency and increasrange of "the curve of approaching,resonance is more gradual. The great advantage of this, aside from the ordinary mechanical advantage of moving slight mass instead of large mass, is that the curve representing the valuesof resonant response for varying frequencies extends far down'the range among the resonant frequencies characteristic of the vowel 1 transmission over long lines.

sounds of articulate speech. 3 hus the resonance curve of increasing mechanical resonace causing increasing magnifying distortion of the higher of these vowel frequencies tends to compensate for and correct the oppositeattenuating distortion which attends This characteristic action of my repeaters in correctingby mechanical resonance the distortion due to thecharacteristics of the line is so marked that loading coils now commonly used for preventing line distortion have beengproved by me to be entirely unnecesdistances up to Obviously, my

sary'for transmission over many thousands of miles.

method of correction of such distortion is from my repeaters,

enormously less expensivethan the loaded line method of prevention. Moreover, as I have pointed out in my Patent No. 1,198,214.; the great power of the reproduced currents renders practicable and useful the correction of line distortion by the leakage method, in lieu of by the inductance, or loading coil method.

In case of the application of. my invention to existing commercial lines already sponse "thereby raising loaded with inductance coils should result inany undue magnification of the resonant vowel frequencies, this may easily be corrected by raising the free period of the vibratory system so as to raise the entire range of the frequencies of resonant reto a required degree. A possible but less desirable method of correction is to increase the inertia of the vibratory system thereby sharpening the resonance curve and the lower limits of resonant response to a higher range, although in practice a judicious combination of increasing ing weight to sharpen the resonance curve and thus raise the lower limit'of the range of resonant response, may sometimes be employed to advantage.

I claim:

1. In a two-way talking telephone system, and in combination with the various .elements thereof including transmitter, re-

ceiver and line, arepeater of the electro-' magnet-microphone type having a mechani-' cally vibratory element or system hav ng a definite harmonic vibration and means for supply ing current tovsaid microphone,the polarity free period of practically simple of the connections of the repeater with said current supply and with the line being se- 'lectedsothat the mechanical phase displacement in the repeater willoein the direction to ba ance o-r compensate for phase displacement elsewhere in the system.

2. In a two-way talking telephone system, and in combination with the various elements thereof including transmitter, receiver and line, a repeater of the electromagnet-microphone type having a mechanica'lly vibratory element or system having a definite free period of practically simple harmonic vibration at frequencies as lll h as one-thousand or more eriods er second, and me'ansfor supplying current to .said microphone, the polarity of the connections of the repeater ,withsaid battery and with the line being selected so that the mechanical phase displacement in the re peater will be in the direction to balance or compensate for electrical phase displacement elsewhere in the system.

3. In a tWo-way-talking telephone system, and in combination with the-various elements thereofincluding transmitter, receiver and line, a repeater of the electro magnet-microphone type having a mechani cally vibratory element'or system having a definite free period of practically simple harmonic vibration and a battery for supplying current to larity of the connections of the repeater with said batteryand with the line being selected so that the mechanical phase displacesaid microphone, the poment in'the repeater will be in the direction to balance or compensate for electrical phase displacement due to the electrical characteristics of the system.

4. In a two-way talking telephone system, elements thereof including transmitter, receiver and line,'a repeater'of the electromagnet-microphone type having a mechanically vibratory element or system having a definite free period of practically simple and in combination with the various harmonic vibration and a batteryfor supplying current'to said microphone, the polarity of the connections of the repeater with said battery and with the line .being selected so that the mechanical phase displacement in the repeater will-be in the direction to balance or compensate for electrical phase displacement due to the electrical characteristics of the system.

16 j and practically but ,or range of resonant response,

,cuits connected in tween the balanced manner as not to disturb. their balance, and

In a reciprocal or twoway talking, two" v repeater clrcuit, separate main line sections .pro'vlded with. phase balancing and current b alancing extensions, twin repeaters'and cirreciprocal relation bemainline sections in such so as to neutralize on the receiving side of each repeater the retransmitted 'current from the'output side of the other repeater, said repeaters being of the electro-magnet-micra phone type-having mechanical vibratory sysjte-Ins of practically the same natural frequency, the connections of one --repeater' to it'sbattery 'orto itssupply circuit. being reversed with respectlto the corresponding;

" connections ofthe other repeater ;"thereby establishing electromechanical phase rela- 'tions in the two repeaters such that incase of singing, one ofthem will 'generateits' with 'phase balancing and current balancing extensions, twin repeaters and circuits connected in reciprocal relation between the balanced main line' sections in such manner,

as not to disturb their balance and so as to neutralize on the output side of the other repeater, said repeaters being of the electro magnet-microphone type having mechanical-vibratory sys tems comprising practically identical values repeater' to its battery or to its line circuit with phase balancing and current balancing being reversed 'sponding connections of the other repeater, so that the electromechanical phase displace: ment in the one compensates with' respect to the correfor and balances the electromechanical phase displace-' .ment in the other.

7'; In a reciprocalor two-way talking, two repeater circuit, main line sectlons provlded extensions, twin repeaters and circuits connected in reciprocal relation between the balanced main as not to disturb their balance, and so as to neutralize on the receiving side of each repeater the retransmitted current from the output side of the other repeater, said repeaters being of the 'electromagnet-microphone type having their respective mechanical vibratory systems composed of-practically identical, identicallyrelated inertia and elasticity elements 'so organized that they have practically the same free period one and the and that, at a minimum frequency of approximately one thousand periods per second, the connections of one repeater to its battery or to its troinechanical receivingside of. eachgre- -peater the retransmitted current from the line sections in such manner,

same region balances the electromechanical phase displacement in .the other.

repeater circuit, mam line sections provided Y with phase balancing and current balancing extensions, twin repeaters and circuits con- 'nected in reciprocal relation between .the balanced main line sections in such manner as not to disturb their balance, and

so as to 8., Ina reciprocal or two-way talking, two,

neutralize on the receiving side of each rea peater the retransmitted current from the output side-of the-other repeater, said repeaters being of the electromagnet-micro phone type having substantially identical, identically adjusted mechanical vibratory systems both constructedso as to have but one region (n-frequency range of resonant its battery or to its line circuit being reversed with respect tothe corresponding connections of the other repeater, so that the electromechanical .phase displacement in the one compensates'.-fo r and balances the elecother..

of speech and correction of distortion in long telephone lines which method consists in countervailing the electrical distortion line by mechanical reso-j occurring in, the

p fnance of one of the electrical translating deand identical relatlons of-their nertia and elasticity elements,- theconnections of one vices of the system.

sion ofspeech and correction of distortion in longtelephone lines which methodconsists in countervailing'the electrical distor- -'tion occurring in theline by utilizing current traversing the line to generate and transmit amplified waves of similar form through the medium vibratory element having a range of 'increasing mechanical" resonant response for the higherof the resonant frequency compo-'- 'nents of theyvowel sounds of iarticulate speech.

11. The method of speech transmission lines which consists in opposing the elec gtrical distortion of the line by the distortion of'mechanical resonance. v r

12. The method of speech transmission and correction of distortion in telephone lines which trical distortion of the line for higher speech frequencies by the distortion of me chanical resonance for such frequencies.

13. The; combination with a telephone line and'a source of current, of a repeater provided with a ment, and connections for the repeater to the line and current source, said repeater The method of t'e'lephonic transmission of a simple harmonic.

vibration,- the connecti-onsof one repeater to phase displacement in the" a 10. The method bf telephonic transmis consists inopposing'the elecmechanical vibratory eleand correction of dlstortlon' in telephone mechanical phase distortion in the repeater -will be in the direction tocompensate for electrical phase distortion' elsewhere in the system.

14:. The combination with a telephone line and a source of current, of a repeater provided-With a mechanical vibratory element having a definite free'period of practically simple harmonic vibration,

I and current source, said repeater and connections illeluding means whereby the mechanical phase distortion in the repeater will be in the direction to compensate forelectrical phase distortion elsewhere in the system.

15. In a telephone circuit, balanced line sections, twin repeaters and circuits conand connections 'for the repeater to the line.

nected in reciprocal relation between the line sections so that their balance is not disturbe'd, said repeaters having mechanical vibratory systems comprising practically identi cal values and identical relations of their inertia and elasticity elementgancLline and battery connections for the repeaters, the connections of one repeater to its battery or to its line circuit.being reversed with respect to the corresponding connectionsof the 1 other repeater so that the electromechanical phase displacement in one compensates for the electromechanical phase displacement in the other.

. Signed at New Yorljr city in the county York and State of New York this of Negv 2d day of June A. D. 1916.

' ELWOOD GRISSINGER. 

